When flying you use the phonetic alphabet when you are in contact with a tower. When contacting a tower you would say something like Lima November Hotel Oscar Romeo (LN-HOR) approaching Rygge airport requesting permission for landing.

Here you can see the whole phonetic alphabet.

A - Alpha
B - Bravo
C - Charlie
D - Delta
E - Echo
F - Foxtrot
G - Golf
H - Hotel
I - India
J - Juliet
K - Kilo
L - Lima
M - Mike
N - November
O - Oscar
P - Papa
Q - Quebec
R - Romeo
S - Sierra
T - Tango
U - Uniform
V - Victor
W - Whiskey
X - Xray
Y - Yankee
Z - Zulu